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1. ### Thomson Scattering In the Early Universe

Homework Statement Why does Thomson scattering occur in the early universe? Homework Equations $$e^{-} + \gamma \rightarrow e^{-} + \gamma$$ is a Thomson scattering process if: $$E_{\gamma} << m_{e}c^{2}$$ (Electrons are essenitally stationary) The Attempt at a Solution [/B] Very...
2. ### Transforming to a Rotating Reference Frame

Homework Statement Let $\mathbf{r}$ be the position of a point in a rigid body relative to some origin $O$. Let $\mathbf{R}$ be the position of the centre of mass from that origin. $\mathbf{r^{*}} = (\mathbf{r}-\mathbf{R})$. $d\boldsymbol{\phi}$ is the infitesimal vector directed...
3. ### Link between 'time' component of 4-momentum and energy

Sure, sure - the units are important and I entirely agree that $p^{0}c$ has the correct units of energy. What I find confusing is not the units, but the idea that somehow a translation in time is related to my classical picture of energy :)

20. ### Two variable function, single integral

Thanks LCKurtz t=tan(\frac{x}{2}) works. Had completely forgotten about that, silly me :P
21. ### Two variable function, single integral

Homework Statement Evaluate: I(y)= \int^{\frac{\pi}{2}}_{0} \frac{1}{y+cos(x)} \ dx if y > 1 Homework Equations The Attempt at a Solution I've never seen an integral like this before. I can see it has the form: \int^{a}_{b} f(x,y) dx I clearly can't treat it as one half of an exact...